Several conventional techniques are employed for seismic analysis of the strata below the bottom of the ocean. Further, the U.S. Geological Service has ruled that seismic sources cannot be detonated so as to unduly disturb the bottom of the ocean. Hence, prior art approaches currently used provide for explosions to occur above the bottom of the ocean and below the bottom of the ocean. For example, drilling rigs are used to drill holes several hundred feet deep so that explosive charges can be placed therein for generation of the seismic source signal. Likewise, in shallow areas, poles are used to implant explosive seismic charges in the soft sediments below the mudline of the ocean bottom. These two prior art approaches are expensive and time consuming. Such approaches, however, are accurate in that they precisely place the seismic source according to a survey technique.
Other conventional approaches relate to exploding seismic charges above the bottom of the ocean so as not to disturb the bottom. Other prior art approaches involved dropping time fused and weighted explosive charges over the side of the boat. With these approaches, however, the time and location of the explosion is not known with the necessary precision for seismic exploration.
Likewise, other prior art approaches use seismic detectors on or near the ocean bottom. For example, the seismic detector can be pulled along in the ocean water, or it can be placed on the bottom of the ocean and anchored thereto by some sort of buoy and anchoring system. Drilling holes, however, to insert detectors into the ocean bottom, although used on land, have not been used extensively in the ocean.
A search of the prior art was made and the following patents were uncovered:
______________________________________ Inventor U.S. Pat. No. Issue Date ______________________________________ C. Shepard 56,623 July 24, 1866 J. Mangold et al 695,068 March 11, 1902 C. E. Bannister 2,717,656 Sept. 13, 1955 D. G. Moore 3,078,931 Feb. 26, 1963 S. Epstein et al 3,373,400 March 12, 1968 Calvin B. Craig 3,561,546 Feb. 9, 1971 Hall, Jr. 3,931,453 Jan. 6, 1976 ______________________________________
The search was directed to devices for implanting seismic devices into the ocean's bottom.
The 1866 patent issued to Shepard (U.S. Pat. No. 56,623) sets forth a well tube and an apparatus for driving or sinking it into the ground. A number of weights are utilized around the tube to provide weight to the tube. The tube is then turned and the weight causes the tube to enter the ground.
The 1902 patent issued to Mangold et al (U.S. Pat. No. 695,068) relates to an apparatus for obtaining deposits from the beds of rivers and the like. A weight is utilized on a guide rod which is affixed to a tube-shaped deposit container. The apparatus is lowered off the side of the boat and, because of the appended weight, engages the ground to obtain samples. The apparatus is then returned to the boat.
The 1955 patent issued to Bannister (U.S. Pat. No. 2,717,656) relates to an apparatus for seismic exploration wherein an aircraft is utilized to lower a tube-shaped penetrating tool. The tool has a weighted head and is dropped from a sufficient elevation to impact and penetrate the ground surface.
The 1963 patent issued to Moore (U.S. Pat. No. 3,078,931) relates to an apparatus for extracting earth core samples from the ocean floor. The Moore apparatus is dropped into the ocean and automatically descends to the ocean's floor, extracts the sample core, and returns to the surface of the ocean to be picked up. The core apparatus includes a weighted core cutting tube which is expendable and once implanted in the ocean floor is not retrieved. The core sample, however, is returned with the remaining portion of the core.
The 1968 patent issued to Epstein et al (U.S. Pat. No. 3,373,400) relates to an apparatus for determination of the geophysical properties of the sea bottom. A sediment probe instrument is dropped into the ocean. The probe is designed to orient itself and to penetrate into the sediment of the ocean bottom a predetermined distance. An explosive charge is placed at the bottom of the probed portion for selective detonation. Additionally, once the probe is implanted, a float is disengaged to rise and to uncoil a cable contained within the probe. Disposed along the cable are a number of explosive charges which are placed between the float and the top of the implanted probe. A timer contained within the probe causes the explosive charges to be selectively detonated. The first charge releases the float and causes the second charge to fall to the mudline of the sea bottom. The second charge is then detonated. Finally, a third detonation pulse is emitted to detonate the explosive charge implanted in the sea sediment.
The 1971 patent issued to Craig (U.S. Pat. No. 3,561,546) sets forth an apparatus for underwater geochemical prospecting by taking samples from submerged areas. A weighted probe is set forth which impacts the bottom of the submerged area to permit the taking of the sample. The probe can then be recovered and the sample removed.
The 1976 patent issued to Hall, Jr. (U.S. Pat. No. 3,931,453) relates to an improved cable anchor case.